Isomerism

Isomers – Organic molecules with same molecular formula but different arrangement of atoms

Two types of Isomerism

Structural Isomerism • Same molecular formula • Different structural formula • Different arrangement of atoms

Hydrocarbon Chain Isomer • Different hydrocarbon chain skeleton

Stereoisomerism • Same molecular formula • Same structural formula • Different spatial arrangement of atoms

Positional Chain Isomer • Different functional group position

Functional Group Isomer • Different functional group

Geometric Isomers

Optical Isomers

Cis Isomers Atoms are located on

the same side

Trans Isomers Atoms are located on

the different side

CH3 -CH –CH2 –CH3 │

OH

CH3 -CH –CH –CH3 │

OH

CH3 –CH2–CH2 – O – CH3

CH3 -CH –CH2 –CH3 | OH

CH3 - CH – CH2 │ |

CH3 OH

CH3 -CH –CH2 –CH3 │

OH

Isomers – Organic molecules with same molecular formula but different arrangement of atoms

Structural Isomerism for C4H9OH • Same molecular formula

• Different structural formula • Different arrangement of atoms

Hydrocarbon Chain Isomer • Different hydrocarbon chain skeleton

Positional Chain Isomer

• Different functional group position

Functional Group Isomer • Different functional group

CH3 –CH2 –CH2 –CH3 │

OH

CH3 –CH2 –CH –CH3 │

OH

CH3 - CH – CH2 – OH │

CH3

CH3 │ CH3 - C – OH │

CH3

CH3 –CH2 –CH2 –CH3 │

OH

CH3 –CH2–CH2 – O – CH3

CH3 –CH2 – O – CH2 -CH3

Butan – 1-ol 2- Methylpropan-1-ol

2- Methylpropan-2-ol

Butan – 1-ol Butan – 2- ol

Butan – 1-ol Methoxypropane Ethoxyethane

Structural Isomerism

CH3 –CH2 –CH2 –CH3 │

OH

H │ CH3 –CH2– C=O

O ║ CH3 – C– CH3

Structural Isomers for C4H9OH – All have same Molecular Formula but different Structural Formula

Isomers – Organic molecules with same molecular formula but different arrangement of atoms

Structural Isomerism

CH3 –CH2 –CH2 –CH2 │

OH

CH3 –CH2 –CH –CH3 │

OH

CH3 - CH – CH2 – OH │

CH3

CH3 │ CH3 - C – OH │

CH3

CH3 –CH2–CH2 –O – CH3

CH3 –CH2 –O– CH2 -CH3

C4H9OH C4H9OH C4H9OH

C4H9OH

C4H9OH C4H9OH

Structural Isomers for C4H9Br – All have same Molecular Formula but different Structural Formula

CH3 –CH2 –CH2 –CH2 │

Br

CH3 –CH2 –CH –CH3 │

Br

CH3 - CH – CH2 – Br

│

CH3

CH3 │ CH3 - C – Br

│

CH3

Structural Isomers for C3H6O – All have same Molecular Formula but different Structural Formula

OH │ CH3 –CH = C-H

OH │ CH2 =CH - C-H2

CH3 – O – CH = CH2

C4H9Br C4H9Br C4H9Br

C4H9Br

C3H6O C3H6O C3H6O C3H6O C3H6O

Structural Isomerism

Isomers – Organic molecules with same molecular formula but different arrangement of atoms

Structural Isomers for C4H8

CH3 –CH = CH –CH3

CH2 = CH –CH2 –CH3

CH3 –CH2 –CH2 –CH2 │

OH

Structural Isomers for C4H10O

CH3 –CH2 –CH –CH3 │

OH

Hydrocarbon Chain Isomer • Different hydrocarbon chain skeleton

Positional Chain Isomer • Different functional group position

Functional Group Isomer • Different functional group

CH3-CH–CH2–OH │

CH3

CH3 │ CH3 - C – OH │ CH3

CH3-CH2-CH2-O–CH3

CH3 -CH2 –O–CH2-CH3

CH3–CH–O–CH3

|

CH3

CH3 –C=CH2

| CH3

CH2 – CH2

| | CH2 - CH2

Ether gp Alcohol gp Alcohol gp

Alkene gp Alkene gp Alkene gp Cycloalkane gp

Structural Isomers for C4H8O

CH3 –CH2 –CH2 –C-H ║

O

CH3– CH – C-H | ║ CH3 O

CH3 –CH2 –C –CH3

║ O

CH2 =CH–CH2–CH2-OH

CH3 -CH = CH –CH2-OH

CH3 –CH2 -CH=CH-OH

CH3–CH2 -O- CH=CH2

CH3–CH =CH-O- CH3

Structural Isomers for C3H6O2

CH3–CH2 –C-OH ║ O

CH3 –C- O-CH3

║ O

H-C-O-CH2-CH3

║ O

CH2- CH = CH

| | OH OH

CH = CH–O–CH3

| OH

CH2 = C–O– CH3

| OH

CH2– CH-OH

CH -OH

Structural Isomerism

Aldehyde group

Ketone group

Alcohol + Alkene group

Ether + Alkene group

Carboxyl group

Ester group

Dialcohol + Alkene gp Ether , Alkene + Alcohol gp

CH2- C =CH2

| | OH OH

CH =C –CH3

| | OH OH

CH2 = CH–O–CH2

| OH

HO-C=CH–CH3

| OH

HO-CH-CH=CH2

| OH

CH3-O-CH2–C-H

║ O

OH | CH3-CH–C-H

║ O

OH | CH2-CH2–C-H

║ O

Aldehyde + Alcohol gp

Aldehyde + ether gp

CH3 –CH2–CH2–CH2-CH2-CH3

Structural Isomerism

Structural Isomers for C6H14

CH3 –CH–CH2–CH2-CH3

| CH3

CH3 –CH2–CH–CH2-CH3

| CH3

CH3

| CH3 –C-CH2-CH3

| CH3

CH3 –CH–CH -CH3

| | CH3 CH3

Structural Isomers for C5H10

CH2 =CH–CH2-CH2-CH3

CH3-CH=CH-CH2-CH3

CH2 =C–CH2-CH3

| CH3

CH2=CH–CH-CH3

| CH3

CH3-CH=C-CH3

| CH3

CH3–CH- CH-CH3

CH2

CH2– CH- CH2-CH3

CH2

CH3

| CH2– C-CH3

CH2

CH2 – CH-CH3

| | CH2– CH2

C H2

CH2 CH2

| | CH2 –CH2

Alkene group Cycloalkane group

Structural Isomerism

Structural Isomers for C5H11Br

CH3 –CH2–CH2–CH2-CH2 Br

CH3 –CH–CH2–CH2-Br

| CH3

CH3 –CH2–CH–CH2-Br

| CH3

CH3 -CH2–CH2–CH-CH3

| Br

CH3

| CH3–CH–CH-CH3

| Br

CH3

| CH3–CH2–C-CH3

| Br

CH3 -CH2–CH–CH2-CH3

| Br

CH3

| CH3 –CH2- C-Br

| CH3

CH3 CH3

| | CH3– C- CH2

| Br

Are these different isomers too?

No

CH3–CH–CH-Br

| | CH3 CH3

CH3

| CH3 –C-CH2-Br

| CH3

same

Structural Isomerism

Structural Isomers for C4H8O2

CH3-CH2-CH2 –C-OH ║ O

CH3-CH – C-OH | ║ CH3 O

CH3 –C- O-CH2-CH3

║ O

H–C- O-CH2-CH2-CH3

║ O

CH3–CH2–C- O-CH3

║ O

CH2- CH2-CH = CH

| | OH OH

CH2- CH=CH- CH2

| | OH OH

CH2- CH-CH =CH2

| | OH OH

CH2- C =CH- CH3

| | OH OH

CH = C - CH2- CH3

| | OH OH

CH3- C = C - CH3

| | OH OH

CH2 = C - CH- CH3

| | OH OH

CH3

| CH = C –CH2

| | OH OH

CH2

║ CH2 - C -CH2

| | OH OH

OH | CH3-CH2-CH–C-H

║ O

OH | CH3-CH-CH2–C-H

║ O

OH | CH2-CH2-CH2–C-H

║ O

OH | CH3-C – C-H

| ║ CH3 O

OH | CH2-CH – C-H

| ║ CH3 O

CH3-O-CH2- CH2–C-H

║ O

CH3CH2-O- CH2–C-H

║ O

CH3

| CH3-O- CH–C-H

║ O

CH = CH-CH2 –O–CH3

| OH

CH = CH –O–CH2-CH3

| OH

CH2 = C-CH2 –O–CH3

| OH

CH2 –CH=CH –O–CH3

| OH

CH3–CH=CH–O–CH2

| OH

CH2 - CH-OH

| | CH2 – CH-OH

CH2 - CH-OH

| | HO-CH – CH2

Carboxyl gp

Ester gp

Cyclic dialcohol gp

Alkene + dialcohol gp

Alkene + Ether + Alcohol gp Aldehyde + ether gp Aldehyde + Alcohol gp

Any more isomers that you can draw?